1. Technical Field
The present invention relates to methods and apparatus for data storage and retrieval particularly, but not essentially, in conjunction with optical disc storage devices.
2. Related Art
Recent years have seen a great expansion in the complexity of consumer electronics equipment with several different proprietary and technical standards governing interconnectivity and data storage. In connection with the latter feature, the domestic user has had to put up with using different mechanical and functional configurations of storage device for different types of equipment, such as a VHS cassette for video recording, an audio compact cassette for audio recordings from Hi-Fi equipment, and floppy discs for data storage on personal computers. With the advent of recordable optical discs conforming to unified standards as far as data layout, bit rates etc. are concerned, such discs may (if configured to the particular recording system) replace many of the disparate options, and hence the possibility of a single unified standard, both in terms of physical configuration and data management, may be contemplated for all types of domestic audio/video/data-processing systems. Whilst each specific application will have its own particular requirements, the physical record carriers to be used (whether optical discs or some other device) should increasingly be capable of use with more than just a single system or medium.
It is therefore an object of the present invention to provide a scheme for data storage on a medium readable by devices of different functionalities, with not only effective partitioning of files between applications, but also inherent inter-connectivity such as to permit, at least in a limited fashion, handling of files from one application by apparatus effecting a different application.
In accordance with the present invention there is provided a storage device containing a memory space to be accessed by a first read/write apparatus, the memory space being partitioned into an array of fragments, at least some of which are read/write accessible by the first apparatus, and containing a contents table for the fragments stored at a predetermined location within the memory space, said table being updateable by said first apparatus; characterised in that at least some fragments are read/write accessible by a second apparatus, to the exclusion of the first apparatus, and the contents table is arranged to indicate for each fragment whether it carries data from the first or the second apparatus or whether it is free and available for use by either. By holding indication in the contents table of the using device/apparatus for each fragment, two file systems may peacefully co-exist in a single storage device, such that unused storage space from one application is not wasted, but instead may be made available to another device which, though physically compatible with the storage device, functions in a different manner to that device initially utilising the storage.
The storage device may be in the form of an optical disc, and data written to fragments (which fragments are suitably of a common size) by the first apparatus may comprise digitised audio and/or video material with the contents table entries in respect of those fragments comprising playlists for the material. The above-mentioned second apparatus may be a data processing apparatus (such as a personal computer) for which the contents table may comprise a logical volume descriptor for those fragments available to the second apparatus.
In use, one of the above-mentioned first and second apparatuses is suitably assigned precedence such that it may overwrite fragments in the storage device already used by the other. The contents table may include identifiers for fragments used by the first apparatus in a format supported by the second apparatus, whereby the second apparatus is enabled to identify fragment usage of the first apparatus.
The present invention also provides a method for formatting memory space in a storage medium to be accessed by a first read/write apparatus comprising the steps of: partitioning the medium into an array of fragments at least some of which are read/write accessible by the first apparatus; and generating a contents table for the fragments and storing the same at a predetermined location within the memory space, said table being updateable by said first apparatus; characterised in that at least some fragments are read/write accessible by a second apparatus, to the exclusion of the first apparatus, and the contents table is arranged to indicate for each fragment whether it carries data from the first or the second apparatus or whether it is free and available for use by either.
Further in accordance with the present invention there is provided a data processing apparatus operable to implement the foregoing method, said apparatus comprising means arranged to receive and format the memory space in said storage medium to be subsequently accessed by said data processing apparatus, the formatting means being configured to partition the medium into an array of fragments at least some of which are read/write accessible by the first apparatus, and to generate a contents table for the fragments, store the same at a predetermined location within the memory space, and periodically update the same; characterised in that the apparatus is further arranged to assign at least some of the fragments as read/write accessible by a second apparatus, and to place in the contents table an indication for each fragment whether it carries data from the data processing apparatus or the second apparatus or whether it is free and available for use by either.